如何从对象数组中获取键和子键？

Question

我有下面这个对象数组。

const array = [{
  field1: "val1",
  field2: "val2",
  field3: {
    field1: "val1",
    field2: "val2"
  }
},
{
  field1: "val1",
  field2: "val2",
  field3: {
    field1: "val1"
  }
}]

我需要获得以下输出。

const output = [{
  key: "field1",
  subkeys: []
},
{
  key: "field2",
  subkeys: []
},
{
  key: "field3",
  subkeys: ["field1", "field2"]
}]

我可以使用这个方法获取顶级字段

const keys = array.map(x => Object.keys(x)[0]);

但无法访问内部元素。

请帮忙……谢谢！！！

- Dark Knight

---

你的对象只有两个层级吗？ - Nina Scholz

@DarkKnight：您期望的输出是什么？const output = [[{key: "field1", subkeys: [] }, {key: "field2", subkeys: [] }, {key: "field3", subkeys: ["field1", "field2"] }], [{key: "field1", subkeys: [] }, {key: "field2", subkeys: [] }, {key: "field3", subkeys: ["field1"] }]]这是一个二维数组吗？还是问题中提到的那个？ - Dhivya Dandapani

如问题所述，不是一个数组的数组。 - Dark Knight

@DarkKnight：谢谢。但是到目前为止被选中的答案似乎没有返回预期的答案。您还在寻找准确的答案吗？ - Dhivya Dandapani

@DarkKnight：你能否提供一个多层嵌套的JSON输入输出示例？我已经发布了一个答案。根据您的要求，我可以进行修改。 - Dhivya Dandapani

Answer 1

你可以在顶层对一个对象键的数组进行缩减，然后检查该键的值是否为对象——如果是，则获取它的嵌套键；否则留下空的子键数组。

const array = [{
  field1: "val1",
  field2: "val2",
  field3: {
    field1: "val1",
    field2: "val2"
  }
},
{
  field1: "val1",
  field2: "val2",
  field3: {
    field1: "val1"
  }
}]

const result = array.map(item => {
  return Object.keys(item).reduce((acc, rec) => {
    if(typeof item[rec] === 'object') {
      return [...acc, {key: rec, subkeys: Object.keys(item[rec])}] 
    }
    return [...acc, {key: rec, subkeys: []}]
  }, [])
})

console.log(result)

- elvira.genkel

---

只是一个小问题...它能否适用于未知的级别？ - Dark Knight

@DarkKnight 对于未知级别的函数应该使用递归。reduce 应该被写成一个函数，并且在 typeof 新子节点是对象的条件下 - 只需运行递归即可。 - elvira.genkel

请注意reduce ({...spread})反模式。 - Moritz Roessler

Answer 2

您可以通过查找嵌套对象来进行任何深度的映射。

const
    getKeys = object => Object.keys(object).map(key => ({ 
        key, 
        subkeys: object[key] && typeof object[key] === 'object'
            ? getKeys(object[key])
            : []
    })),
    array = [{ field1: "val1", field2: "val2", field3: { field1: "val1", field2: "val2" } }, { field1: "val1", field2: "val2", field3: { field1: "val1" } }];

console.log(array.map(getKeys));

.as-console-wrapper { max-height: 100% !important; top: 0; }

- Nina Scholz

Answer 3

这个解决方案使用了lodash库。我已经提取了变量以便更好的可读性。这个解决方案适用于2级。

const array = [
    {"field1":"val1","field2":"val2","field3":{"field1":"val1","field2":"val2"}},
    {"field1":"val1","field2":"val2","field3":{"field1":"val1","field4":"val1"}}
];

intermediateOutput = array.reduce(
  (accumulator, entry) => _.merge(accumulator, entry),
{});
// intermediateOutput = {"field1":"val1","field2":"val2","field3":{"field1":"val1","field2":"val2","field4":"val1"}}

const finalOutput = _.map(_.keys(intermediateOutput), (key) => {
  const value = intermediateOutput[key];
  return {key, subkeys: _.isObject(value) ? _.keys(value): [] }
})

console.log(finalOutput);
// finalOutput = [{"key":"field1","subkeys":[]},{"key":"field2","subkeys":[]},{"key":"field3","subkeys":["field1","field2","field4"]}]

- Dhivya Dandapani

---

其实我有一个对象数组 https://lodashfiddle.herokuapp.com/ka6dpidr/ ...。我需要这些键保持不变，但是值为空字符串。 - Dark Knight

@DarkKnight：感谢您提供的lodashfiddle。在fiddle中发布的数组似乎格式不太正确。另外，如果您在lodashfiddle中发布的数组的注释中也提到预期输出，那将会更有帮助。 - Dhivya Dandapani

Answer 4

const output = []
for (let [key, value] of Object.entries(array)) {
    const subkeys = Object.keys(value)
    output.push({key, subkeys})
}

类似这样的内容？

- Abraham Labkovsky